JP2007110827A - Inverter device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inverter device wherein a smoothing means whose output voltage largely pulsates is used yet current distortion in a motor is suppressed. <P>SOLUTION: The inverter device includes a voltage command compensating means 11 that superposes a result obtained by the following processes on a voltage command value such that: the amplitude and phase of a frequency signal obtained by multiplying the product of the number of pole pairs of a motor 5 and the number of revolutions of the motor 5 by an integer are adjusted by the phase (actual number of revolutions) of the motor 5, a current command value, and the phase of the output voltage of the smoothing mean 3. Voltage command compensation including a phase computation error caused by a pulsating voltage is carried out, and the smooth driving of the motor 5 in which current distortion in the motor 5 is suppressed is thereby accomplished. Thus, current distortion in the motor 5 can be suppressed irrespective of pulsation in the output voltage of the smoothing means 3. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a current flowing through an electric motor in an inverter device in which a smoothing means composed of an extremely small capacitor and reactor is connected to the output terminal of the rectifying means and the output voltage pulsates greatly at twice the frequency of the AC power supply frequency. The purpose is to suppress the distortion of the motor and drive the motor more smoothly.

  Conventionally, in an inverter device having a voltage command compensation means for calculating a compensation amount (amplitude) of a voltage command value based on a current command value, the output voltage pulsates greatly at a frequency twice the AC power supply frequency for cost reduction and miniaturization. When such a smoothing means is used, the current distortion of the electric motor cannot be sufficiently suppressed.

FIG. 6 shows a block diagram of an inverter device having a voltage command compensation function of a conventional inverter device. Generally, a voltage command value (amplitude) is compensated by a current command value, and an inverter device is operated (for example, refer to Patent Document 1).
JP-A-9-84385

  However, in the driving of the inverter device having the above-described conventional configuration, when smoothing means is used such that the output voltage pulsates greatly at twice the frequency of the AC power supply frequency, a phase calculation error of the electric motor 5 due to the pulsating voltage occurs, and the electric motor 5 There is a problem that current distortion of the current cannot be sufficiently suppressed.

  SUMMARY OF THE INVENTION The present invention solves the above-described conventional problems, and an object thereof is to provide an inverter device that suppresses current distortion of an electric motor while using a smoothing means that pulsates with a large output voltage.

  In order to solve the conventional problems, an inverter device according to the present invention includes a rectifier that rectifies an AC power supply, a smoother that pulsates an output voltage from the rectifier, and a current detector that detects a current of the motor. Phase calculating means for calculating the rotational phase of the electric motor based on the detection value of the current detecting means, and current command calculating means for calculating a current command value from the indicated rotational speed and the actual rotational speed calculated from the phase calculating means Voltage command calculation means for calculating a voltage command value based on the current command value and the detection value of the current detection means, and a frequency signal obtained by multiplying the product of the number of pole pairs of the motor and the motor rotation number by an integer. An inverter device characterized by comprising voltage command compensation means for superimposing on a command value, whereby the output voltage from the smoothing means pulsates greatly at twice the frequency of the AC power supply frequency Oite, by performing the voltage command compensation, including the phase calculation errors due to pulsation voltage can achieve smooth motor drive which suppresses current distortion of the electric motor.

  ADVANTAGE OF THE INVENTION According to this invention, the inverter apparatus which can implement | achieve suppression of the electric current distortion of an electric motor irrespective of the output voltage pulsation of a smoothing means can be provided.

The first invention is based on a rectifying means for rectifying an AC power supply, a smoothing means for pulsating an output voltage from the rectifying means, a current detecting means for detecting a current of the electric motor, and a detection value of the current detecting means. Phase calculation means for calculating the rotation phase of the electric motor, current command calculation means for calculating a current command value from the indicated rotation speed and the actual rotation speed calculated from the phase calculation means, the current command value and the current detection means Voltage command calculation means for calculating a voltage command value based on the detected value, and voltage command compensation means for superimposing a frequency signal obtained by multiplying a product of the number of pole pairs of the motor and the motor rotation number by an integer on the voltage command value. In the inverter device in which the output voltage from the smoothing means pulsates greatly at twice the frequency of the AC power supply frequency, a phase calculation error due to the pulsating voltage is included. By performing the pressure command compensation can be achieved a smooth motor drive which suppresses current distortion of the electric motor.

  According to a second invention, in the inverter device of the first invention, the voltage command compensation means is capable of adjusting at least one of an amplitude and a phase of a signal to be superimposed on the voltage command value. Even when an error occurs, the current distortion of the motor can be suppressed by voltage command compensation.

  According to a third invention, in the inverter device of the first or second invention, the voltage command compensation means is a signal to be superimposed on the voltage command value in accordance with at least one change in the rotational speed of the motor, the detected current value, and the current command value. It is characterized in that at least one of the amplitude and phase of the motor is adjusted, and even when a phase calculation error occurs due to a pulsating voltage, the current distortion of the motor can be suppressed by voltage command compensation according to the error level. I can do it.

  According to a fourth aspect of the present invention, in any one of the first to third inverter devices, the inverter includes a voltage phase calculation unit that calculates a pulsating voltage phase output from the smoothing unit, and the voltage command compensation unit sets the voltage phase value to the voltage phase value. It is characterized in that at least one of the amplitude and phase of the signal to be superimposed on the voltage command value is varied, and the amplitude and phase of the compensation signal to the voltage command can be adjusted according to the phase calculation error due to the pulsating voltage It becomes possible, and suppression of current distortion of the electric motor can be realized.

  According to a fifth aspect of the present invention, in any one of the first to fourth inverter devices, the voltage command compensation means superimposes a frequency signal obtained by multiplying the product of the number of pole pairs of the motor and the motor rotation speed on the voltage command value. It is possible to suppress current distortion of the motor due to dead time in PWM switching control.

  According to a sixth aspect of the present invention, in any one of the first to fifth inverter devices, the smoothing means includes a capacitor and a reactor, and a resonance frequency obtained from the capacitor and the reactor is 40 times or more the AC power supply frequency. It is characterized by the above setting, and high performance of the power supply harmonic characteristics of the input current to the rectifying means can be realized.

  A seventh invention is characterized in that, in any one of the first to sixth inverter devices, a film capacitor is used as a capacitor constituting the smoothing means, and the influence on the life characteristics due to temperature is concerned. You can select the usage environment.

  According to an eighth aspect of the present invention, the air conditioner has any one of the first to seventh inverter devices, and the size and cost of the device can be reduced by reducing the capacity of the condenser and reactor constituting the smoothing means. Therefore, it is possible to realize high performance of the power supply harmonic characteristics of the input current to the rectifying means.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 is a control block diagram of an inverter device according to an embodiment of the present invention. The inverter device is supplied with electric power from an AC power source 1 such as a commercial power source that is a single-phase AC power source, and includes a rectifying unit 2 configured by a diode bridge for full-wave rectification of the supplied AC power source, and the rectifying unit 2 The output voltage from the smoothing means 3 pulsates greatly at twice the frequency of the AC voltage, and an orthogonal circuit composed of a semiconductor switching element that converts the output voltage from the smoothing means 3 into a desired AC voltage for driving the motor 5. It has the conversion means 4 and the current detection means 6 for detecting the electric current which flows into the electric motor 5.

  Further, the phase calculation means 7 for calculating the rotation phase of the electric motor 5 based on the detection value from the current detection means 6, and the electric motor 5 based on the externally indicated rotation speed and the actual rotation speed calculated from the phase calculation means 7. A current command calculating means 8 for calculating a current command value for driving, a voltage command calculating means 9 for calculating a voltage command value based on the current command value and the detected current value, and driving an orthogonal transformation means from the voltage command value. PWM signal generating means 10 for generating a signal to be transmitted, voltage phase calculating means 12 for calculating the phase of the pulsating voltage output from the smoothing means 3, and a frequency obtained by multiplying the number of pole pairs of the motor 5 and the number of rotations of the motor 5 by an integer. Voltage command compensation means 11 is provided that varies the amplitude / phase of the signal according to the detected current value, the motor phase, the current command value, the pulsating voltage phase, etc., and superimposes it on the voltage command value.

  Here, the compensation signal output from the voltage command compensation means 11 is not limited to a sine wave waveform but includes all cyclic repetitive waveforms. Furthermore, the current detection means 6 is not limited to directly detecting the phase current of the electric motor 5 with a current sensor or the like, but includes estimation detection from the bus current of the orthogonal transform means 4. Further, the smoothing means 3 includes a capacitor having a small capacity of 0.4 μF or more and 100 μF or less set so that the resonance frequency is 40 times or more of the AC power supply frequency, and a peak value of the inrush charging / discharging current to the capacitor. It has a reactor with a small capacity of 2 mH or less for lowering. Since the reactor constituting the smoothing means 3 is inserted between the AC power source 1 and the capacitor constituting the smoothing means 3, it may be either before or after the rectifying means 2.

  About the inverter apparatus comprised as mentioned above, the operation | movement and an effect | action are demonstrated below.

  First, FIG. 2 shows changes in the command value before and after the voltage command compensation means 11 in the present embodiment. FIG. 2 shows the voltage command value before compensation output from the voltage command calculation means 11, the compensation signal output from the voltage command compensation means 11, and the voltage command value input to the PWM signal generation means 10 after compensation. .

  As described above, a voltage command value obtained by superimposing a compensation signal that is an integral multiple (5 times) of the voltage command value on the voltage command value output from the voltage command calculation unit 9 is input to the PWM signal generation unit 10. Thus, the current distortion of the electric motor 5 caused by the influence of the dead time is suppressed.

  Next, the amplitude and phase of the compensation signal from the voltage command compensation means 11 will be described with reference to FIGS. First, the pulsation of the output voltage from the smoothing means 3 will be described.

  When a commercial power supply with an AC power supply frequency of 50 Hz is used as the AC power supply 1, the values of the reactor and the capacitor constituting the smoothing means 3 are such that the resonance frequency fc = 1 / (2π × √ (L1 × C1)) is the AC power supply frequency. Is set to be 40 times or more, that is, 2000 Hz or more. Therefore, by using a reactor and a capacitor having a reactance value of 0.5 mH and a capacitance value of 10 μF, fc (= 2250 Hz)> 40 × AC power supply frequency (50 Hz) is satisfied.

Thus, by significantly reducing the capacitor capacity of the smoothing means 3, as shown in FIG. 3, it pulsates greatly (ripple ratio 80% or more) at twice the AC power supply frequency. Thus, when the output voltage from the smoothing means 3 pulsates greatly, the compensation signal from the voltage command compensation means 11 adjusts the phase and amplitude according to the pulsating voltage phase. 3 shows the compensation signal 1 from the voltage command compensation means 11, the compensation signal 2 having a phase different from that of the compensation signal 1, and the compensation signal 3 having an amplitude different from that of the compensation signal 2. FIG.

  For example, as shown in FIG. 3, the voltage phase is divided into 1 to 3 sections, the compensation signal 3 in the section 1, the compensation signal 2 in the section 2, the compensation signal 1 in the section 3, and the phase By outputting compensation signals having different amplitudes from the voltage command compensation means and superimposing them on the voltage command value, it is possible to effectively suppress current distortion of the electric motor 5.

  Next, the amplitude / phase adjustment of the compensation signal according to the rotation speed of the electric motor 5 will be described with reference to FIG. Here, FIG. 4 shows the rotation speed of the electric motor 5, the compensation signal 1 from the voltage command compensation means 11, and the compensation signal 2 having a phase different from that of the compensation signal 1. For example, as shown in FIG. 4, when the rotational speed of the electric motor 5 changes from state 1 to state 2, the phase corresponds to the compensation signal 1 in state 1 and compensation signal 2 in state 2 according to each rotational speed state. By outputting the compensation signal from the voltage command compensation means 11 and superimposing it on the voltage command value, the distortion of the current of the electric motor 5 can be effectively suppressed.

  Next, the amplitude / phase adjustment of the compensation signal based on the current command value and the current detection value will be described with reference to FIG. Here, FIG. 5 shows a current command value or a current detection value, a compensation signal 1 from the voltage command compensation means 11, a compensation signal 2 having a phase different from that of the compensation signal 1, and a compensation signal 3 having an amplitude different from that of the compensation signal 2. For example, as shown in FIG. 5, when the current command value transitions from state 1 to state 2, in state 1, the compensation signal 1 and in state 2, the compensation signal 3 and the amplitude / By outputting the compensation signals having different phases from the voltage command compensation means and superimposing them on the voltage command value, the distortion of the current of the electric motor 5 can be effectively suppressed.

  As described above, in the present embodiment, the voltage command for superimposing the compensation signal whose amplitude and phase are adjusted by the pulsating voltage phase, the motor rotation speed, the current command value, and the current detection value output from the smoothing means 3 on the voltage command value. By providing the compensation means 11, it is possible to realize driving in which the current distortion of the motor is suppressed in the inverter device in which the output voltage from the smoothing means 3 pulsates greatly at twice the frequency of the AC power supply frequency.

  As described above, the inverter device according to the present invention suppresses the distortion of the motor current, and can reduce the cost and size of the device. Therefore, the inverter device according to the present invention has all types of motors that are required to reduce the cost and size of the device. Applicable to inverter device.

Control block diagram of inverter device in Embodiment 1 of the present invention Comparison waveform diagram before and after the command of the voltage command compensation means Operation waveform diagram of the voltage command compensation means Other operation waveform diagrams of the voltage command compensation means Other operation example waveform diagram of same voltage command compensation means Control block diagram of conventional inverter device

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 AC power supply 2 Rectification means 3 Smoothing means 4 Orthogonal transformation means 5 Electric motor 6 Current detection means 7 Phase calculation means 8 Current command calculation means 9 Voltage command calculation means 10 PWM signal generation means 11 Voltage command compensation means 12 Voltage phase calculation means 12

Claims (8)

Rectifying means for rectifying the AC power supply, smoothing means for pulsating the output voltage from the rectifying means, current detecting means for detecting the current of the motor, and the rotational phase of the motor based on the detection value of the current detecting means. Based on the phase calculation means for calculating, the current command calculation means for calculating the current command value from the indicated rotation speed and the actual rotation speed calculated from the phase calculation means, the current command value and the detection value of the current detection means Voltage command calculation means for calculating a voltage command value; and voltage command compensation means for superimposing a frequency signal obtained by multiplying the product of the number of pole pairs of the motor and the motor rotation number by an integer on the voltage command value. Inverter device. 2. The inverter device according to claim 1, wherein the voltage command compensation means can adjust at least one of an amplitude and a phase of a signal to be superimposed on the voltage command value. The voltage command compensation means adjusts at least one of an amplitude and a phase of a signal to be superimposed on the voltage command value in accordance with at least one change in the rotational speed of the motor, the detected current value, and the current command value. The inverter device according to 1 or 2. Voltage phase calculating means for calculating the pulsating voltage phase output from the smoothing means is provided, and the voltage command compensating means varies at least one of amplitude and phase of a signal to be superimposed on the voltage command value based on the voltage phase value. The inverter device according to any one of claims 1 to 3. 5. The inverter according to claim 1, wherein the voltage command compensation means superimposes a frequency signal obtained by multiplying a product of the number of pole pairs of the motor and the motor rotation speed by about 5 times on the voltage command value. 6. apparatus. The smoothing means includes a capacitor and a reactor, and a resonance frequency obtained from the capacitor and the reactor is set to be 40 times or more of an AC power supply frequency. The described inverter device. The inverter device according to any one of claims 1 to 6, wherein a film capacitor is used as a capacitor constituting the smoothing means. An air conditioner provided with the inverter device according to any one of claims 1 to 7.

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